CN111490666A - PWM modulation method, module and PWM control system - Google Patents
PWM modulation method, module and PWM control system Download PDFInfo
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- CN111490666A CN111490666A CN202010097324.7A CN202010097324A CN111490666A CN 111490666 A CN111490666 A CN 111490666A CN 202010097324 A CN202010097324 A CN 202010097324A CN 111490666 A CN111490666 A CN 111490666A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
- H02M3/33515—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with digital control
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0012—Control circuits using digital or numerical techniques
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- Dc-Dc Converters (AREA)
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Abstract
The invention provides a PWM (pulse-width modulation) method, a module and a PWM control system. According to the PWM modulation method, under the condition that the PWM period is not changed, the pulse width is adjusted for multiple times in one PWM period, the power switch tube is dynamically controlled, the limit of low working frequency of the power switch tube is overcome, and the quick response of an object (a power supply system) controlled by the power switch is realized.
Description
Technical Field
The invention relates to the field of insulated gate bipolar transistor control, in particular to a PWM (pulse-width modulation) method, a module and a PWM control system.
Background
The existing industrial-grade high-power supply (tens of Kw to hundreds of Kw grade) is usually assembled by adopting a high-power Insulated Gate Bipolar Transistor (IGBT) module. The IGBT has the characteristics of energy conservation, convenience in installation and maintenance, stability in heat dissipation, large working current and the like, and is widely applied. The large power supply basically selects Insulated Gate Bipolar Transistor (IGBT), such as a ferroelectric motor drive, a motor control of an electric automobile and the like. Therefore, it is important to control the IGBT to achieve a fast response of the power supply system. In the prior art, an analog power control chip and a digital power control chip are mostly adopted to control the IGBT. The analog power control chip is mostly realized by series of UC38XX, SG25XX, and the like. The digital power control chip is mainly realized by adopting a TI28XX series to control the IGBT. However, due to the limitation that the operating frequency of the power switching tube including the IGBT is low, even when the operating frequency of the analog power control chip and the digital power control chip is high, a quick response of an object (power supply system) controlled by the power switch cannot be realized.
Disclosure of Invention
The invention aims to provide a PWM (pulse-width modulation) method, a PWM module and a PWM control system, so as to realize quick response of an object (a power supply system) controlled by a power switch.
In order to achieve the purpose, the invention provides the following scheme:
a PWM modulation method, comprising the steps of:
setting the maximum pulse width of the initial current PWM period as the actual modulation pulse width of the last PWM period, setting the initial value of a time count value as 0, and increasing the time count value by 1 from the initial value every preset time period;
acquiring a PID calculation result, and calculating a given pulse width of the current PWM period according to the PID calculation result;
acquiring a time count value during AD sampling as a current time count value;
judging whether the current time count value is smaller than the maximum pulse width of the current PWM period or not to obtain a first judgment result;
if the first judgment result indicates that the current time count value is smaller than the maximum pulse width of the current PWM period, judging whether the current time count value is smaller than the given pulse width of the current PWM period to obtain a second judgment result, if the second judgment result indicates that the current time count value is smaller than the given pulse width of the current PWM period, updating the maximum pulse width of the current PWM period by using the given pulse width of the current PWM period, performing PWM modulation by using the updated maximum pulse width of the current PWM period to obtain the actual modulation pulse width of the current PWM period, and returning to the step of obtaining a PID calculation result and calculating the given pulse width of the current PWM period according to the PID calculation result;
and if the first judgment result shows that the current time count value is not less than the maximum pulse width of the current PWM period or the second judgment result shows that the current time count value is not less than the updated maximum pulse width of the current PWM period, waiting for the arrival of the next PWM period, and when the next PWM period arrives, executing the steps of setting the initial pulse width of the current PWM period as the actual modulation pulse width of the previous PWM period and setting the initial value of the time count value as 0.
Optionally, the performing PWM modulation by using the updated maximum pulse width of the current PWM period to obtain the actual modulation pulse width of the current PWM period specifically includes:
when the time count value is increased, judging whether the increased time count value is smaller than the updated maximum pulse width of the current PWM period to obtain a third judgment result;
if the third judgment result shows that the increased time count value is smaller than the updated maximum pulse width of the current PWM period, setting the PWM modulation signal to be at a high level;
and if the third judgment result shows that the increased time count value is not less than the updated maximum pulse width of the current PWM period, setting the PWM modulation signal to be at a low level, and setting the updated maximum pulse width of the current PWM period as the actual modulation pulse width of the current period.
A PWM modulation module, the PWM modulation module comprising: the device comprises a PWM counter, a PWM value updating module and a PWM generating module;
the PWM counter is connected with the PWM value updating module and is used for counting time and sending a time count value to the PWM value updating module;
the PWM value updating module is connected with the PWM generating module and is used for obtaining a PID calculation result, calculating the given pulse width of the current PWM period according to the PID calculation result, judging whether the current time counting value is smaller than the maximum pulse width of the current PWM period or not, and judging whether the current time counting value is smaller than the given pulse width of the current PWM period or not when the current time counting value is smaller than the maximum pulse width of the current PWM period; when the current time count value is smaller than the given pulse width of the current PWM period, updating the maximum pulse width of the current PWM period by using the given pulse width of the current PWM period, performing PWM modulation by using the updated maximum pulse width of the current PWM period to obtain the actual modulation pulse width of the current PWM period, and sending the updated modulation pulse width to the PWM generation module;
the PWM generating module is connected with the PWM counter and used for carrying out PWM modulation by using the updated modulation pulse width and the time count value of the PWM counter, acquiring the actual modulation pulse width of the current PWM period and sending the actual modulation pulse width of the current PWM period to the PWM value updating module.
Optionally, the PWM generating module includes a comparator and a comparison result processing sub-module;
the comparator is used for judging whether the increased time count value is smaller than the updated maximum pulse width of the current PWM cycle or not when the time count value is increased, and obtaining a third judgment result;
the comparison result processing submodule is used for setting the PWM modulation signal to be at a high level if the third judgment result shows that the increased time count value is smaller than the updated maximum pulse width of the current PWM period; and if the third judgment result shows that the increased time count value is not less than the updated maximum pulse width of the current PWM period, setting the PWM modulation signal to be at a low level, and setting the updated maximum pulse width of the current PWM period as the actual modulation pulse width of the current period.
A PWM control system comprises an AD sampling module, a PID calculation module, a PWM modulation module, a power switch tube assembly and a control object;
the AD sampling circuit is respectively connected with the control object and the PID calculation module, and the AD sampling module is used for collecting a state signal of the control object and sending the state signal to the PID calculation module;
the PID calculation module is connected with the PWM modulation module and is used for carrying out PID calculation on the state signal to obtain a PID calculation result and sending the PID calculation result to the PWM modulation module;
the PWM module is connected with the power switch tube assembly, the power switch assembly is connected with the control object, and the PWM module is used for carrying out PWM according to the PID calculation result to obtain a PWM signal and controlling the power switch tube by utilizing the PWM signal so as to control the state of the control object.
Optionally, the PID calculation module is an incremental PID calculation module.
Optionally, the control object is a dc power supply, and the dc power supply includes a transformer and a rectifier.
Optionally, the AD sampling module includes a voltage hall sensor, a current hall sensor, and an AD converter;
the voltage Hall sensor and the current Hall sensor are both arranged on the secondary side of the transformer, and the voltage Hall sensor is used for acquiring the secondary output voltage of the transformer; the current Hall sensor is used for acquiring secondary output current of the transformer;
the voltage Hall sensor is connected with the AD converter, the current Hall sensor is connected with the AD converter, and the AD converter is connected with the PWM modulation module.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention provides a PWM (pulse-width modulation) method, a module and a PWM control system. According to the PWM modulation method, under the condition that the PWM period is not changed, the pulse width is adjusted for multiple times in one PWM period, the power switch tube is dynamically controlled, the limit of low working frequency of the power switch tube is overcome, and the quick response of an object (a power supply system) controlled by the power switch is realized.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a flow chart of a PWM modulation method according to the present invention;
FIG. 2 is a schematic diagram of the counting provided by the present invention;
FIG. 3 is a schematic diagram of a PWM modulation method according to the present invention;
FIG. 4 is a schematic diagram of a parameter relationship provided by the present invention;
FIG. 5 is a clock diagram of a PWM modulation method according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a conventional PWM method according to the present invention;
FIG. 7 is a flow chart of the maximum pulse width update for the current PWM cycle provided by the present invention;
FIG. 8 is a schematic diagram of PWM modulation using the updated maximum pulse width of the current PWM cycle according to the present invention;
FIG. 9 is a schematic structural diagram of a PWM control system according to the present invention;
fig. 10 is an AD sampling clock diagram of an AD sampling module provided in the present invention;
fig. 11 is an AD sampling schematic diagram of an AD sampling module provided in the present invention;
FIG. 12 is a schematic diagram of PID calculation of the PID calculation module provided by the present invention;
fig. 13 is a PID calculation clock diagram of the PID calculation module provided by the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a PWM (pulse-width modulation) method, a PWM module and a PWM control system, so as to realize quick response of an object (a power supply system) controlled by a power switch.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
As shown in fig. 1, the present invention provides a PWM modulation method, which includes the steps of:
the maximum pulse width Tp (K0) of the initial current PWM period is set to the actual modulation pulse width U (0) of the last PWM period, and the initial value of the time count value Tc, which is increased by 1 every preset time period from the initial value, is set to 0.
And acquiring a PID calculation result u, and calculating the given pulse width Tg of the current PWM period according to the PID calculation result.
The time count value Tc at the time of AD sampling is acquired as the current time count value.
And judging whether the current time count value Tc (K1) is smaller than the maximum pulse width Tp (K0) of the current PWM period or not to obtain a first judgment result.
If the first determination result indicates that the current time count value Tc (K1) is smaller than the maximum pulse width Tp (K0) of the current PWM period, determining whether the current time count value Tc (K1) is smaller than the given pulse width Tg (K1) of the current PWM period, obtaining a second determination result, if the second determination result indicates that the current time count value Tc (K1) is smaller than the given pulse width Tg (K1) of the current PWM period, updating the maximum pulse width of the current PWM period, that is, Tp (K1) ═ Tg (K1), performing PWM modulation by using the updated maximum pulse width Tp (K1) of the current PWM period, obtaining the actual modulation pulse width U (1) of the current PWM period, returning to the step "obtaining a PID calculation result, and calculating the given pulse width of the current PWM period according to the PID calculation result".
And if the first judgment result shows that the current time count value Tc (K1) is not less than the maximum pulse width Tp (K0) of the current PWM period or the second judgment result shows that the current time count value Tc (K1) is not less than the given pulse width Tg (K1) of the current PWM period, waiting for the coming of the next PWM period, and when the next PWM period comes, executing the steps of setting the initial maximum pulse width of the current PWM period as the actual modulation pulse width of the previous PWM period and setting the initial value of the time count value as 0.
For convenience of description, the PERIOD (preset time PERIOD) of the time count value Tc is set to 1/200 MHZ-5 ns, the maximum value of Tc is set to PWM _ MAX _ PERIOD, and the Tc updating process is as shown in fig. 2.
The principle of the PWM modulation method provided by the present invention is shown in fig. 3. The parameters Tc, Tg, and Tp are shown in fig. 4, where Tc is the time count value of the counter of PWM, Tp is the maximum pulse width of PWM in the present period — the PWM pulse width (maximum pulse width) updated last time, and Tg is the calculation result of PID — which corresponds to the given pulse width. If the cycle is a PWM signal, the PWM outputs '1' when D > is 0, and outputs '0' when D < 0.
The PWM modulation method of the present invention is explained below with specific examples, and the calculation frequency of the PID of the present invention is much higher than the PWM frequency. The present invention is illustrated with a PWM frequency of 20KHZ and a PID calculation period of 200KHZ, as shown in FIG. 5.
The existing PWM modulator updating period is only one time at K0, and the PWM value of the period is not changed no matter how the values of K1-K10 are changed before the next PWM period comes. As shown in fig. 6, when the counter time K0 is Tc ═ 0, if the maximum value (corresponding to the maximum pulse width) Tg (K0) is given as TMAX after PID calculation, the value is given as the input value of PWM, and the PWM pulse width of one period is finally generated after the input value is given to the PWM generating module. The PWM counter Tc is then incremented by 0+1 … K1 at 1/200MHz each time until the time PWM _ MAX _ PERIOD arrives.
Tp(K0)＝Tg(K0)＝Tmax；
As can be seen from fig. 6, the PWM state "1" at time T1 is definite and cannot be changed. The PWM state "1" (maximum value Tmax calculated by PID at the start Tc ═ 0) in time T2 may be changed since PWM is waiting to be executed. And the basis for the change is the value calculated by PID at Tg (K1). Remaining adjustment range of PWM pulse width: Tp-Tc (K1).
As shown in fig. 5, when the counter time Tc is set to "Tc (K1)", the operating principle of the PWM update determination of "Tg (K1)" is given after PID calculation:
(1) when the time counter Tc (K1) <tg (K0) (Tg (K0) is the result of PID calculation at the time of the last K0, the maximum pulse width Tp (K0) at the time of the last K0). I.e., allow pulse width updates-reset the PWM output in real time. It can be seen that the PWM update of the present invention does not need to wait until the next period K0(Tc ═ 0) comes. The update speed is greatly advanced.
The updated principle is shown in FIG. 7, where the value of the PWM counter is judged at time counter "K1" to be compared with the value of PID at K1:
when the Tc (K1) <Tg (K1) time is K1, the PWM pulse width is adjusted to Tp (K1) <Tg (K1)
When the Tc (K1) > Tg (K1) time is K1, the PWM pulse width is adjusted so that Tp (K1) becomes 0, i.e., the PWM output is "0".
(2) When the time counter Tc (K1) > Tg (K0) (Tg (K0) is the result of PID calculation at the time of the last K0), the PWM pulse is turned off, i.e., the PWM output is not allowed to be turned on again in the present period, and the frequency of 20KHZ must be guaranteed to be stable.
In the case where the PWM signal is turned off, the PWM is no longer allowed to turn on, otherwise the frequency cannot be guaranteed to be constant (e.g., 20 KHZ).
(3) Four times, K2, K3, K4, K5 and so on (repeating the above processes (1) and (2)) until the end of the cycle, that is, 5 times of updating is allowed at maximum.
The PWM signal must ensure that the PWMA and PWMB widths are consistent or that magnetic bias is caused, so once the PWMA pulse width is fixed, the PWMB pulse width is fixed. I.e. K5, K6, K7, K8, K9, K10 are also not allowed to be updated.
The PWM modulation is performed by using the updated maximum pulse width of the current PWM period to obtain the actual modulation pulse width of the current PWM period, and specifically includes: when the time count value is increased, judging whether the increased time count value is smaller than the updated maximum pulse width of the current PWM period to obtain a third judgment result; if the third judgment result shows that the increased time count value is smaller than the updated maximum pulse width of the current PWM period, setting the PWM modulation signal to be at a high level; and if the third judgment result shows that the increased time count value is not less than the updated maximum pulse width of the current PWM period, setting the PWM modulation signal to be at a low level, and setting the updated maximum pulse width of the current PWM period as the actual modulation pulse width of the current period.
The principle of PWM modulation using the updated maximum pulse width of the current PWM PERIOD is shown in fig. 8, where Tc is a PWM counter, and when the maximum count value reaches PWM _ MAX _ PERIOD, Tc is set to 0.
localparamPWM _ PERIOD ═ 13' b1_1111_0100_ 0000; // PWM period
localparamPWM _ dead ═ 16'd 1000; // PWM dead zone definition;
localparamPWM _ DEARD1 ═ 16'd 1000; // PWM dead zone definition;
localparamPWM_MAX_PERIOD＝PWM_PERIOD+PWM_DEARD*2；
localparamPWM_MAX_PERIOD1＝PWM_PERIOD+PWM_DEARD1*2。
as shown in fig. 9, the present invention further provides a PWM modulation module, which includes: the device comprises a PWM counter, a PWM value updating module and a PWM generating module; the PWM counter is connected with the PWM value updating module and is used for counting time and sending a time count value to the PWM value updating module; the PWM value updating module is connected with the PWM generating module and is used for obtaining a PID calculation result, calculating a given pulse width of a current PWM period according to the PID calculation result, judging whether a current time counting value is smaller than the maximum pulse width of the current PWM period, judging whether the current time counting value is smaller than the given pulse width of the current PWM period when the current time counting value is smaller than the maximum pulse width of the current PWM period, updating the maximum pulse width of the current PWM period by using the given pulse width of the current PWM period when the current time counting value is smaller than the given pulse width of the current PWM period, carrying out PWM modulation by using the updated maximum pulse width of the current PWM period, obtaining an actual modulation pulse width of the current PWM period, and sending the updated modulation pulse width to the PWM generating module; the PWM generating module is connected with the PWM counter and used for carrying out PWM modulation by using the updated modulation pulse width and the time count value of the PWM counter, acquiring the actual modulation pulse width of the current PWM period and sending the actual modulation pulse width of the current PWM period to the PWM value updating module.
The PWM generation module comprises a comparator and a comparison result processing submodule; the comparator is used for judging whether the increased time count value is smaller than the updated maximum pulse width of the current PWM cycle or not when the time count value is increased, and obtaining a third judgment result; the comparison result processing submodule is used for setting the PWM modulation signal to be at a high level if the third judgment result shows that the increased time count value is smaller than the updated maximum pulse width of the current PWM period; and if the third judgment result shows that the increased time count value is not less than the updated maximum pulse width of the current PWM period, setting the PWM modulation signal to be at a low level, and setting the updated maximum pulse width of the current PWM period as the actual modulation pulse width of the current period.
As shown in fig. 9, the present invention further provides a PWM control system, which includes an AD sampling module, a PID calculating module, a PWM modulating module, a power switching tube assembly and a control object; the AD sampling circuit is respectively connected with the control object and the PID calculation module, and the AD sampling module is used for collecting a state signal of the control object and sending the state signal to the PID calculation module; the PID calculation module is connected with the PWM modulation module and is used for carrying out PID calculation on the state signal to obtain a PID calculation result and sending the PID calculation result to the PWM modulation module; the PWM module is connected with the power switch tube assembly, the power switch assembly is connected with the control object, and the PWM module is used for carrying out PWM according to the PID calculation result to obtain a PWM signal and controlling the power switch tube by utilizing the PWM signal so as to control the state of the control object.
The A/D sampling object of the AD sampling module is divided into primary side pulse current, secondary side output current and secondary side output voltage. If the power supply is flat (constant voltage), PID operation is performed by using the sampling voltage (data) to control the pulse width of the PWM signal. And outputting a voltage signal by using the voltage Hall sensor to participate in operation.
If the power supply has steep drop characteristic (constant current characteristic), PID operation is carried out by sampling secondary output current (data) to control the pulse width of the PWM signal. And the current Hall sensor is used for outputting a voltage signal to participate in operation.
The clock of the AD sampling is shown in fig. 10, and the principle of the AD sampling is shown in fig. 11. T0 Power-on initialize- -all registers, I/O states, etc. of the A/D conversion portion are initialized. T1 carries out the first A/D sampling and transmits to PID input interface to take part in operation. And T2 carries out second A/D sampling and transmits the second A/D sampling to the PID input interface to participate in operation. And the TN carries out Nth A/D sampling and transmits the Nth A/D sampling to the PID input interface to participate in operation. Until the power is turned off. Therefore, the state of the controlled object (power supply) can be mastered in real time by the high-speed uninterrupted sampling FPGA chip.
The PID calculation module of the invention is an incremental PID calculation module. The recursive form of the incremental PID is shown in fig. 12, and the clock of the incremental PID is shown in fig. 13.
As shown in fig. 11 and 12, u (k) ═ u (k-1) + △ u (k);
△u(k)＝Kp*(e(k)-e(k-1))+Ki*e(k)+Kd*(e(k)-2*e(k-1)+e(k-2))；
e(k)＝r(k)-s(k)；
wherein e (K) is an input deviation value at the Kth sampling time;
e (K-1) is the deviation value of the input of the sampling time of the K-1 th time (last time);
u (k) is a PID output result of this time, wherein the PID output result range is (0) -4096, and u (k) is 0, no PID output exists, and no PWM output exists correspondingly; u (k) ═ 4096 — corresponds to the maximum PID output, and to the widest PWM output.
u (k-1) -last PID output result.
u (k1) is the first PID calculation and output result, and this time parameter is saved.
And u (k2) comprehensively calculating the PID according to the first parameter value and the current sampling data for the second time, outputting the result, and storing the current parameter.
u (kn) calculating PID according to the parameter value of the last time and N sampling data in the Nth time and outputting the result until the power supply is turned off.
Kp-proportionality coefficient;
TI-integration constant;
ki integral coefficient;
kd differential coefficient;
k — sample sequence number, K0, 1,2,3,4, … …;
r (K) -the Kth given sampling value-an upper computer (a computer or a singlechip) is transmitted to a receiving module of the FPGA through a communication interface RS 232.
s (K) -th feedback sample value-data sampled using the a/D sampling part of the FPGA, determined using the characteristics of the power supply from which the type of data sampled (current data or voltage data) is based.
The AD sampling data range is (0- - -4096); constant current power supply: 0- -no current, 4096- -corresponds to maximum current; constant voltage power supply: 0- -no voltage, 4096- -corresponds to the highest voltage.
K0 is power-on initialization — all registers of the initialized PID part, u (K) 0, u (K-1) 0, e (K-1) 0, e (K-2) 0;
the control object of the present invention is a direct current power supply including a transformer and a rectifier, but not limited to a direct current power supply. At the moment, the AD sampling module comprises a voltage Hall sensor, a current Hall sensor and an AD converter; the voltage Hall sensor and the current Hall sensor are both arranged on the secondary side of the transformer, and the voltage Hall sensor is used for acquiring the secondary output voltage of the transformer; the current Hall sensor is used for acquiring secondary output current of the transformer; the voltage Hall sensor is connected with the AD converter, the current Hall sensor is connected with the AD converter, and the AD converter is connected with the PWM modulation module.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention provides a PWM (pulse-width modulation) method, a module and a PWM control system. According to the PWM modulation method, under the condition that the PWM period is not changed, the pulse width is adjusted for multiple times in one PWM period, the power switch tube is dynamically controlled, the limit of low working frequency of the power switch tube is overcome, and the quick response of an object (a power supply system) controlled by the power switch is realized.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (8)
1. A PWM modulation method, characterized by comprising the steps of:
setting the maximum pulse width of the initial current PWM period as the actual modulation pulse width of the last PWM period, setting the initial value of a time count value as 0, and increasing the time count value by 1 from the initial value every preset time period;
acquiring a PID calculation result, and calculating a given pulse width of the current PWM period according to the PID calculation result;
acquiring a time count value during AD sampling as a current time count value;
judging whether the current time count value is smaller than the maximum pulse width of the current PWM period or not to obtain a first judgment result;
if the first judgment result indicates that the current time count value is smaller than the maximum pulse width of the current PWM period, judging whether the current time count value is smaller than the given pulse width of the current PWM period to obtain a second judgment result, if the second judgment result indicates that the current time count value is smaller than the given pulse width of the current PWM period, updating the maximum pulse width of the current PWM period by using the given pulse width of the current PWM period, performing PWM modulation by using the updated maximum pulse width of the current PWM period to obtain the actual modulation pulse width of the current PWM period, and returning to the step of obtaining a PID calculation result and calculating the given pulse width of the current PWM period according to the PID calculation result;
and if the first judgment result shows that the current time count value is not less than the maximum pulse width of the current PWM period or the second judgment result shows that the current time count value is not less than the updated maximum pulse width of the current PWM period, waiting for the arrival of the next PWM period, and when the next PWM period arrives, executing the steps of setting the initial maximum pulse width of the current PWM period as the actual modulation pulse width of the previous PWM period and setting the initial value of the time count value as 0.
2. The PWM modulation method according to claim 1, wherein the PWM modulating with the updated maximum pulse width of the current PWM period to obtain the actual modulation pulse width of the current PWM period specifically comprises:
when the time count value is increased, judging whether the increased time count value is smaller than the updated maximum pulse width of the current PWM period to obtain a third judgment result;
if the third judgment result shows that the increased time count value is smaller than the updated maximum pulse width of the current PWM period, setting the PWM modulation signal to be at a high level;
and if the third judgment result shows that the increased time count value is not less than the updated maximum pulse width of the current PWM period, setting the PWM modulation signal to be at a low level, and setting the updated maximum pulse width of the current PWM period as the actual modulation pulse width of the current period.
3. A PWM modulation module, comprising: the device comprises a PWM counter, a PWM value updating module and a PWM generating module;
the PWM counter is connected with the PWM value updating module and is used for counting time and sending a time count value to the PWM value updating module;
the PWM value updating module is connected with the PWM generating module and is used for acquiring a PID calculation result, calculating the given pulse width of the current PWM period according to the PID calculation result and judging whether the current time count value is smaller than the maximum pulse width of the current PWM period; when the current time count value is smaller than the maximum pulse width of the current PWM period, judging whether the current time count value is smaller than the given pulse width of the current PWM period, when the current time count value is smaller than the given pulse width of the current PWM period, updating the maximum pulse width of the current PWM period by using the given pulse width of the current PWM period, performing PWM modulation by using the updated maximum pulse width of the current PWM period, acquiring the actual modulation pulse width of the current PWM period, and sending the updated modulation pulse width to the PWM generation module;
the PWM generating module is connected with the PWM counter and used for carrying out PWM modulation by using the updated modulation pulse width and the time count value of the PWM counter, acquiring the actual modulation pulse width of the current PWM period and sending the actual modulation pulse width of the current PWM period to the PWM value updating module.
4. The PWM modulation module according to claim 3, wherein the PWM generation module comprises a comparator and a comparison result processing submodule;
the comparator is used for judging whether the increased time count value is smaller than the updated maximum pulse width of the current PWM cycle or not when the time count value is increased, and obtaining a third judgment result;
the comparison result processing submodule is used for setting the PWM modulation signal to be at a high level if the third judgment result shows that the increased time count value is smaller than the updated maximum pulse width of the current PWM period; and if the third judgment result shows that the increased time count value is not less than the updated maximum pulse width of the current PWM period, setting the PWM modulation signal to be at a low level, and setting the updated maximum pulse width of the current PWM period as the actual modulation pulse width of the current period.
5. A PWM control system, characterized in that the PWM control system comprises an AD sampling module, a PID calculation module, the PWM modulation module of any one of claims 3-5, a power switch tube assembly and a control object;
the AD sampling circuit is respectively connected with the control object and the PID calculation module, and the AD sampling module is used for collecting a state signal of the control object and sending the state signal to the PID calculation module;
the PID calculation module is connected with the PWM modulation module and is used for carrying out PID calculation on the state signal to obtain a PID calculation result and sending the PID calculation result to the PWM modulation module;
the PWM module is connected with the power switch tube assembly, the power switch assembly is connected with the control object, and the PWM module is used for carrying out PWM according to the PID calculation result to obtain a PWM signal and controlling the power switch tube by utilizing the PWM signal so as to control the state of the control object.
6. The PWM control system of claim 5, wherein the PID calculation module is an incremental PID calculation module.
7. The PWM control system according to claim 5, wherein the control object is a DC power supply including a transformer and a rectifier.
8. The PWM control system of claim 7, wherein the AD sampling module comprises a voltage Hall sensor, a current Hall sensor and an AD converter;
the voltage Hall sensor and the current Hall sensor are both arranged on the secondary side of the transformer, and the voltage Hall sensor is used for acquiring the secondary output voltage of the transformer; the current Hall sensor is used for acquiring secondary output current of the transformer;
the voltage Hall sensor is connected with the AD converter, the current Hall sensor is connected with the AD converter, and the AD converter is connected with the PWM modulation module.
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